Field of the Invention
The invention is related to an illumination apparatus.
Description of the Related Art
Conventionally, in a flash apparatus being an illumination apparatus with variable irradiation angles, a wide panel detachably inserted into a front surface of a light emitting window and a light diffusing adapter detachably attached to the light emitting window are arranged so as to correspond to an angle of view of a super wide angle lens, and emitting light from a light emitting unit is diffused at a super wide angle. An optical action surface including a plurality of quadrangular pyramid protruding portions, on which diffusing process is carried out so as to have diffusing characteristics, is formed on a region corresponding to the light emitting window in a surface on a light emitting unit side of the wide panel and the light diffusing adapter.
For example, in Japanese Patent No. 4592933, a light diffusing adapter covering a light emitting window includes a region corresponding to the light emitting window and a pair of bending portions extending backward from both sides of the region corresponding to the light emitting window. A group of quadrangular pyramid protruding portions is formed on a region corresponding to the light emitting window on a light emitting unit side and a region near the bending portions on an object side.
In Japanese Patent Laid-Open No. 11-344749, a region corresponding to a light emitting window of a light diffusing adapter on an object side is a curved surface. Steps are formed on a region on a light emitting unit side so that all distances from the curved surface on the object side are equal, and a group of quadrangular pyramid protruding portions is formed on each step.
However, in conventional arts disclosed in Japanese Patent No. 4592933 and Japanese Patent Laid-Open No. 11-344749, since a power diffused by a quadrangular pyramid shape is strong, luminance at a center of a screen (hereinafter referred to as “guide number”) drastically decreases.